Recently, mobile information terminal devices which have an interactive communication function and are equipped with a transparent touch panel for information display and information input, which are represented by tablet PCs and smartphones, have been widely distributed not only in Japan but also across the globe.
In spite of the presence of resistance film-type touch panels which are excellent in terms of cost, electrostatic capacitance-type touch panels, particularly, projection electrostatic capacitance-type touch panels have been increasingly demanded as transparent touch panels since gesture operations such as multi-touch are possible and the image quality of ultrahigh-definition display elements is not easily impaired.
In some cases, an anti-glare sheet having an uneven structure is installed on the surface of a touch panel to prevent the reflection of external light.
Furthermore, there are cases in which optical sheets having an uneven structure are used as a base material for the outermost front surface, an internal base material, and a base material for the outermost back surface in a touch panel for the adhesion and prevention of interference fringes between members constituting the touch panel, the adhesion and prevention of interference fringes between the touch panel and display elements, and the like.
However, in a case in which an optical sheet having an uneven structure such as an anti-glare film is used, there is a problem in that the uneven structure causes a phenomenon (scintillation) in which subtle luminance unevenness appears on image light, and display quality degrades. Particularly, in recent display elements having ultrahigh definition (pixel density of 300 ppi or more), the scintillation problem is becoming more serious.
As techniques to prevent scintillation arising from surface unevenness, there have been proposed techniques of the patent documents 1 to 9.